diff --git a/minirag/llm/openai.py b/minirag/llm/openai.py
index 699c8a9..cdb09b8 100644
--- a/minirag/llm/openai.py
+++ b/minirag/llm/openai.py
@@ -101,7 +101,8 @@ async def openai_complete_if_cache(
 ) -> str:
     if api_key:
         os.environ["OPENAI_API_KEY"] = api_key
-
+    if base_url==None:
+        base_url = os.environ["OPENAI_API_BASE"]
     openai_async_client = (
         AsyncOpenAI() if base_url is None else AsyncOpenAI(base_url=base_url)
     )